Electron beam control



May 31, 1960 D. A. WILBUR 2,939,04!l6 ELECTRON BEAM CONTROL Filed June 16, 1958 U 27 V W 4" If: ll /.5 E 2/ /J Fig. 4-

5 5 /n venfor 5 5 Donald A. Wilbur,

His Attorney.

Unite ELECTRON BEAM CONTROL Donald A. Wilbur, Scotia, N,Y., assignor to General Electric Company, a corporation of New York Filed June 16, 1958, Ser. No. 742,106 3 Claims. (Cl. SIS-39.71)

and with different types of interaction structures and with diiferent requirements with respect to the beam shape, densityand velocity, the need for improved means for producing and directing electron beams has in-' creased. In accordance with the present invention a moving beam of electrons is produced by mutually perpendicular electric and magnetic fields and themotion of this cloud of electrons then changed in direction to bring it into desired relationship with an interaction structure or collecting structure by an additional component of magnetic field generally parallel to the electric field. This type of control ofiers advantages of flexibility and simplicity particularly suited for producing a dense beam of electrons which may be moved into interacting relationship with a high frequency structure such as an extended interaction circuit of a traveling wave tubeor the like.

It is accordingly an important object of my invention to provide new and improved electron beam apparatus involving improved beam control under the influence of a combination of electric and magnetic fields.

Further objects and advantages of my invention will become apparent as the following description proceeds, reference being had to the accompanying drawing and its scope will be pointed out in the appended claims. In the drawing Figure l is an elevational View in section of a magnetron type discharge device embodying my invention;

Figure 2 is a sectional view taken along the line 2-2 of Figure 1,

Figure 3 is an elevational view partially in section of a modified form of my invention, and

Figure 4 represents schematically, voltage and magnetic field relationships provided in the illustrated embodiments of the invention.

In Figures 1 and 2 of the drawing I have shown my invention embodied in what may be described as a magnetic injection type magnetron device. In other words, the rotating space charge cloud is produced in a space charge region displaced axially from the high frequency interaction space of the magnetron and the rotating space charge moved into the interaction space by means of a magnetic field generally parallel to the electric field. In the particular arrangement illustrated the magnetic field is in a radial direction. Referring now to Figure 1 of the drawing I have shown my invention embodied in a magnetron type of device including a generally cylindrical envelope made up of alternately arranged conducting or metal terminals -14, inclusive, separated and mutually insulated by generally annular ceramic insulators -48, inclusive. The metal terminals 10 and '14 are in the form of disk-like end caps and provide the support for and electrical connection to a cathode struc- States Patent 2,939,046 Patented May 31, 1960 L2 ture including a generally cylindrical non-emitting portion l9 supported from an integral hub 200a the end ,cap14 andia tungsten spiral 21. One end :of the:spiral 21 is receivedin a centrally locatedrrecess22"inithe end cap 2t and the other end positioned around a reduced endportion 23 of the non-emittingportion19.

A generally cylindrical array'of anode sections surrounds the non-emitting portion :1-9'otthe cathodestruc- .ture and is supported from the terminals 12 and 13. As indicated inithe drawing the anode sections are arranged in alternate relation in two :sets with one set of anode sections 24 connected to and supported .from the terminal 13 while the alternate anode sections .25 provide .the other set and are supported-from anode terminal 12.

;-with respect to cathode terminals. 10; and 14. Also the control electrode 26 and the associated terminal are maintained at a positive volt-age withrespectto the cathode terminal 14 but at a negative voltage with respect to the anodes. A suitable heater voltage is impressed across the cathode terminals 10 and .14 and .as illustrated this is accomplished by utilizingia portion of batitery 30 for that purpose.

It will be understood that theanodetterminals :12 and .13 are, in the operation of the device described, maintained at. the samedirect current voltage and are conv'ne'cted with a suitable high frequency circuitsuchas the oRPOsite side walls of a rectangular ave guide (not shown).

In the operation of the device thus far described a rotating space charge cloud is provided in the region between the emitting cathode 21 and the electrode 26 under the combined action of the axially magnetic field *and the radial electric field. In accordance with the present invention this space charge which is in the form of rotating annular cloud of electrons is moved axially or longitudinally into interacting relation with the anode structure in the region between the anode segments 24 and 25 and the non-emitting cathode 19. This is accomplished by providing a component of magnetic field which is transverse to the direction of motion of the electrons in the rotating electron cloud. Stated in another way, this component of magnetic field is parallel to the electric field which in the specific embodiment illustrated means that it is a radial component of magnetic field. This field may be produced by an auxiliary source of magnetomotive force such as a coil 31 located adjacent the terminal 10 and surrounding the pole piece It is apparent that energization of this coil by a suitable current will provide a magnetomotive force having a component extending radially inwardly in the region between the emitting cathode 21 and the surrounding electrode 26.

In Figure 4 I have illustrated schematically, by vectors B B and E, the components of electric and magnetic fields provided in accordance with the present invention. Vector B represents the axial magnetic field produced by the permanent magnet including pole pieces 27 and 28. B which is directed radially inwardly is produced by the coil 31 and the electric field E is that produced in the space between the cathode 21 and the electrode 26 by means of the battery 30. With this combination of electric and magnetic fields the electrons rotate in the space between the cathode 21 and the electrode 26 and are moved longitudinally or axially into the interaction space between the non-emitting cathode 19 and the anode segments 24 and 25.

In Figure 3 I have shown a modification of my invention in which the component of magnetic field which is parallel to the electric field is produced by the same magnet structure that is employed to produce the axial magnetic field. As illustrated in Figure 3 the pole piece 28' is made of substantially larger diameter than the pole piece 27 with the result that the permanent magnet produces in addition to the component of magnetomotive force in an axial direction as illustrated at B in Figure 4, a component of magnetomotive force directed radially inwardly as illustrated at B in Figure 4.

It will be apparent to those skilled in the art that other arrangements may be employed for producing the magnetic field parallel to the electric field and that the combination of electric and magnetic fields described in accordance with the present invention may be employed for producing a desired injection or movement of an electric beam after it is set in motion by a combination of electric and magnetic fields.

While particular embodiments of my invention have been described it will be apparent to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects and I aim, therefore, in the appended claims to cover all such changes and modifications as fall .within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United'States is:

1. An electron beam system comprising means for generating an electron beam including an electron emitting cathode electrode and a surrounding electrode, means impressing a direct current voltage between said electrodes to produce a space charge cloud in the region between said electrodes, means producing a longitudinal magnetic field component perpendicular to the electric field between said electrodes to cause rotation of said space charge cloud, an interaction structure between said electrodes by said direct current voltage to spaced longitudinally from said electrodes and means producing a magnetic field component parallel to the electric field produced by said direct current voltage to move said rotating space charge longitudinally and into interacting relationship with said interaction structure.

2. An electric discharge device system comprising means for generating anelectron beam including an electron emitting cathode electrode and a surrounding electrode, means impressing a direct current voltage between said electrodes to produce a space charge cloud in the region between said electrode, means producing a longitudinal magnetic field component perpendicular to the electric field between said electrodes to cause rotation of said space charge cloud, a non-emitting cathode spaced longitudinally fromsaid electrodes, a generally cylindrical array of anode segments surrounding said non-emitting cathode, and means producing a magnetic field component parallel to the electric field produced by said direct current voltage to move said rotating space charge longitudinally and into the region between said array of anode segments and said non-emitting cathode.

3 An electric discharge device system comprising means for generating an electron beam including an electron emitting cathode electrode and a spaced electrode, means impressing a direct current voltage between said electrodes to produce a space charge cloud in the region between said electrodes, means producing a magnetic field component perpendicular to the electric field between said electrodes to cause movement of said space charge cloud in a direction perpendicular to the direction of the spacing between said electrons, an electron beam interaction structure spaced from both said electrodes in a direction perpendicular to the spacing between said electrodes and means producing a magnetic field component parallel to the electric field produced move said space charge longitudinally and into interacting relationship with said interaction structure.

References Citedin the file of this patent UNITED STATES PATENTS 2,585,741 Clogston Feb. 12, 1952 

